Vapor phase reaction of n2f4 with certain unsaturated organic compounds

ABSTRACT

1. IN THE ADDITION REACTION OF AN UNSATURATED ORGANIC COMPOUND REACTANT IN VAPOR-PHASE WITH N2F4 TO FORM AN ADDUCT, SAID UNSATRURATED ORGANIC COMPOUND CONTAINING 2 TO 6 CARBON ATOMS AND 1 TO 3 DOUBLE BONDS, THE IMPROVEMENT WHICH COMPRISES ADMIXING N2F4 HAVING A PARTIAL PRESSURE OF 38 TO 380 MM. HG ABS. AT 25*C. WITH THE UNSATURATED ORGANIC REACTANT HAVING A PARTIAL PRESSURE OF 80 TO 380 MM. HG ABS. AT 25*C. AND WITH AN INERT GAS HAVING A PARTIAL PRESSURE AT 25*C. ABOVE THE COMBINED PARTIAL PRESSURES OF THE N2F4 AND ORGANIC REACTANTS TO FORM A GASEOUS REACTION MIXTURE, REACTING THE REACTANTS IN SAID GASEOUS REACTION MIXTURE AT A REACTION TEMPERATURE IN THE RANGE OF ABOUT 20* TO 200*C., AND RECOVERING A RESULTING ADDUCT PRODUCT CONTAINING NF2 GROUPS LINKED TO CARBON IN THE UNSATURATED ORGANIC COMPOUND.

United States PatentO a g. 3555049= VAPOR PHASE REACTION or, F, wrrnCERTAIN UNSATURATEDORGANIC COMPOUNDS I EllingtblrM. Magee, ScotchPlains, N.J., assignor to Esso Research and Engineering Company, acorporation of v. I '-,-;1

No Drawing. Filed Oct. 30,1961, Ser. No.'*149,482

' Int. Cl. C07d 5/00 m V U.S. Cl. 260347.7 e 6 Claims This invention isconcerned with an improvement in the reaction of unsaturated compounds,such as olefinic C to C hydrocarbons and furan, in the vapor-phasewithlow pressure tetrafluorohydrazine,'N F to form adducts by the additionof NF' groups to'carbon atoms linked together in the unsaturatedcompounds by double bonds. It is concerned with carrying out thisreaction at high yield levels, more safely, at reasonable or increasedrates, with lower concentrations of N F and at low reaction tempera- IPrior to the'present invention, it was considered necessary to have theN F reactant'in high concentration and 3,555,049 Patented .lan. 12, 1971i suchas "l,3-butadiene, pentadiene, hexadiene, -hexatrien'e,

cyclohexadiene, benzenefunsaturated cyclic ethers such as furan, andunsaturated organic compounds having functional groups, e.g., vinylisocyanate. In general, the un saturated compound used'as the reactantshould have "a' boiling point below 100 C. so that it and the reactionproduct can'be maintained in the vapor-phase 'under the reactionconditions. These reactants in generalcontainQ to 6 carbon atoms and 1to 3 double bonds per molecule. Suitable inert gases to" be used for thereaction are methane, ethane, carbon"dioxide,* helium and nitrogen.

in excess of the stoichiomet-ric' proportion to'make the additionreaction proceed toward completion andto counteract any tendency of theunsaturated compound to, undergo polymerization. At the same time, itwas deemed necessary'to raise the reaction temperatures to as high alevel as possible in order to havea reasonable rate'of addition,

and it was found that athigh temperatures, N F adducts tend to becomeunstable and that there are greater dam gers'of explosions in avapor-phase reaction mixture.

' Now, in accordance with the present invention, it has been foundpossible to'carry out the vapor-phase addition reaction at lowertemperatures in the'range' ofabout 20 to 200 C., at'which the product ismore stable, by using low concentrations orpartialpressuresof reactantsand suitable'higher proportions "ofinert gas to make the'reac tionproceed smoothly and at a suprising faster rate.

Employing" the teachings of the present invention; rea-' sonable'ratesof theaddition"reaction at lower temperatures or increased-ratesofreaction at any given temperature can be maintained by operating'with'anexcess' of the olefin or unsaturated compound reactantlwith respect tothe N F reactant and with an inert gas added infproportion"substantially higher than the proportion of both re- In carrying out theprocedure of thisfinvention, deterinina tions oftotal pressure 'ofthe'reaction mixture; the

partial pressures'of the reactants,'and the partialpress'ure ofthe'inert'gas are conveniently made at about room temperature,i.e.,"-abo1'1 t'20to 25 C. The pressures stated are absolute'pressures.Proportioning of'the reactants and L of the inert gas is critical'foraccomplishing the reaction within a reasonably shorttime, preferablysubstantially less "25 minutes,fin forming bisfl h adducts'of theunsaturated organic reactants.

In the preferred embodiments Of thevapor-phasereaction increased in rateby inertgas, the partial pressure measured at 25 C. of the' N F reactantintroduced'into the reaction zone is in the range of 3810380 mm. HgabsL, the'partial' pressure at'2 5 C of the unsaturated organ icreactantintroduced into the reactionzoneis a't'lea'st as high as that of'the N Eand in the range'pf 80 to 380 mm. abs, so that thepcombined partialpressures of thereactants measured'at ZSf C. are in the range of 11l8 to760 mmgHg absL'Ihe inert gas admixed with the reactants shduldbe atleast one-half the initial total pressure of thelreactionmixture'andrnay have'partial pressure at '25? Cfin theran'ge of 124 to750mm. Hg abs. or higher. The uppei'limitfotffthe inert gas proportiondependson a variety of factors, such asstrength'and size of the reactor,temperatureof'reaction,and apparatus for no appreciable differences inresults. The reactions were theoretical yield.

mole of the unsaturated organic reactant,

Other inert gases may also be used, e.g., CF; and CCI' F but the inertgases should be preferably a normally gaseous compound which is notreactive under the conditions of reaction and which can be easilyseparated by fractionation from the products.

Generally the reaction temperatures for the addition reaction with theinert gas-diluted, relatively low-pressure reactants are in the range ofabout 20 to 200 C. to prevent undesired side reactions, such as polymerformation, and to prevent a decomposition of the N F which results inthe formation of N nitrogen oxides and CF compounds, i.e., compounds inwhich fluorine is linked to carbon in the resulting organic product.

A series of experiments have shown that the rate of formation of the N Fadducts of olefins is proportional to the partial pressure orconcentration of the olefin and proportional to the square root of thepartial pressure concentration of the N F in an unexpected manner; Thisrelationship has been shown to hold regardless of whether the moleproportion of the N F to the olefin is less than one or greater thanone, and regardless of the presence of inert gas. A demonstration ofthis relationship is given in the following Table I whichsummarizesexperimental conditions and yields, of C H (NF based on the Time,

of carrying out the reaction under steady state conditions in a flowreactorwithin a reasonable time can be obtained 'by using about 0.25 to1 mole proportion of N F per In the foregoing studies, the reaction of NF with vfethylenefwas used as a model reaction. This addition proceedsmore smoothly with little, if any, side reactions in using lower N Fproportions. In various experiments,

batches of N 1; from different sources and different degrees of purity,about 98 to 99% N513}, were use d with carried out essentially in thesame manner with accurate temperature control (about 0.5 C. deviation).The reactions were carried out in different reactors, one of which was aPyrex bulb with a surface/volume ratio of 0.608, and the other was acoil Pyrex reactor tube with a surface/volume ratio of 1.62. It wasdetermined that the wall surface of the reactors did not have anappreciable effect on the rate of reaction.

Two different procedures were used for charging the reactors for testswith and without inert gas admixed.

In a batch procedure, the N F was first added and frozen. Then thereactor was degassed, after which it was warmed up to room temperature(25 C.) and the pressure was recorded, after which the ethylene wasadded, the mixture frozen for degassing and, finally, total pressure atroom temperature (25C.) was determined. Inert gas, when used, was thenadded. Finally, the gaseous mixture was brought to the correct reactiontemperature. In the flow reaction procedure, the reactants, and inertgas if used, were expanded into the reactor from storage bulbs. Thepressures of the gases in the system was followed manometrically.

In using the continuous flow reactor system, the gaseous reactionmixture is passed as a stream through the reaction zone and the adductproduct mixed with unreacted reactants flows continuously from theopposite inlet end of the reaction zone through the outlet of thereactor to means for collecting and separating the higher boiling adductproduct as a condensate from the unreacted gaseous reactants orreactant. With the unsaturated organic compound or olefin used in excessof the stoichiometric proportion with respect to the N F the unsaturatedorganic compound or olefin is separated as a vapor and may be recycledto be admixed with additional N F and passed again through the reactionzone or through another reaction zone. A second flow reactor may be usedin tandem with a first reactor for a second stage of reaction of theunreacted organic reactants or of the partially reacted adduct product.

By operating with varied proportions of the reactants and also byaddition of varying amounts of inert gas, it was determined that therate of reaction depends also on the total pressure and, morespecifically, on the square root of the total pressure. Thus, for agiven initial pressure of olefin and N F the rate is doubled byincreasing the total pressure by a factor of 4 through the addition ofinert gas. This corresponds approximately to an increase of 12 C. (22F.) in reaction temperature. Conversely, if a certain rate is desiredand is obtainable at a certain temperature, then this rate may beobtained at a 12 C. lower temperature by simply increasing the totalpressure by a factor of 4 through addition of inert gas. Accordingly,rates can be maintained by lowering the amount of N F and increasing theamount of inert gas by a similar amount. If the N F concentration isdecreased by a factor of 2 and the total pressure is increased by afactor of 2 through addition of inert gas, then the rate will remain thesame and explosive hazards will be decreased. The following table showsdata supporting the principle of using an inert gas with loweredconcentration of N F for maintaining a desired rate of reaction.

TABLE II.REACTION F 02H; WITH NQFA AT 125 c.

Initial Xkr+ Initial Initial pressure (initial pressure pressure CzHe(Initial k 1O total N 2F C1114 (inert gas) total mmr l presmm. Hg mm. Hgmm. Hg pressure) min: sure) Rate constant expression:Rate=k1(olefin)(N2F4) Rate I:(total pressure) -(olefin) (N F.)

The data in Table II indicate how the inert gas can be used to replace N1 in maintaining a higher rate of reaction. The last column to the rightof Table II shows that the rate constant depends on the (total pressure)The effect of ethane, C H used as an inert gas is nearly the same, asthe pure reactants and products in maintaining a certain rate ofreaction. Other inert gases are not necessarily quite as efficient, e.g.carbon dioxide and nitrogen. The compared effects of different inertgases are shown in the following table.

TABLE III.EFFECI OF INERI GAS *kcule. :2.26 (Pomm-I-Pmzrn) In the lastcolumn of Table III is shown the relative value of the observed rateconstant with respect to a calculated constant, the calculated constantbeing that which would have been arrived at had the inert gas not beenpresent. Helium was found nearly as effective as ethane according totests on a gaseous mixture containing 1.9 moles of olefin to 1 mole of NF and He in a higher proportion to make the value of (Initial TotalPressure) =20.2 mm. with the resulting k 10 =4.02. In plotting the datapoints to determine the rate constants graphically, the data were foundto fit remarkably well.

As another example, a study was made of the vaporphase conversion offuran to the bis(NF adduct. In this study a long coil fiow reactor withseparate preheating sections for N F and furan was used. The furan wasvaporized using, in one instance N F gas, and in another, inert gas, andthe mixture was metered into the coil. The basic laboratory reactor wasdesigned to give 5 minutes contact time at a flow rate of about 1 gramper hour of olefin feed. Actual runs on 'furan were made at contacttimes of 2 to 20 minutes. There were difficulties in vaporizing thefuran mixed with hot N F but in successful runs, furan was mixed with NF at a lower temperature and then vaporized with inert gas, e.g., N

At lower residence time, the flow unit conversion rate of the furan tobis(NF adducts was found to be in agreement with the rate equation whichsets forth that the rate is proportional directly to the concentrationof the olefin employed multiplied by the square root of theconcentration of the N F and further multiplied by the square root ofthe total pressure. It was observed that at low pressures of thereactants without inert gas, the vaporphase conversion of furan to thebis(NF adduct of furan gave rise to severe polymer formation even atrelatively low reaction temperatures, e.g., 150 C., but further runsshowed that by increasing the pressure mainly by addition of inertgaseous diluent, the temperature of reaction could 'be lowered to about100 C. to obtain a high conversion of the furan to the bis adductproduct with decrease in polymer formation.

What is claimed is:

1. In the addition reaction of an unsaturated organic compound reactantin vapor-phase with N F to form an adduct, said unsaturated organiccompound containing 2 to 6 carbon atoms and l to 3 double bonds, theimprovement which comprises admixing N F having a partial pressure of 38to 380 mm. Hg abs. at 25 C. with the unsaturated organic reactant havinga partial pressure of to 380 mm. Hg abs. at 25 C. and with an inert gashaving a partial pressure at 25 C. above the combined partial pressuresof the N F and organic reactants to form a gaseous reaction mixture,reacting the reactants in said gaseous reaction mixture at a reactiontemperature in the range of about 20 to 200 C., and recovering aresulting adduct product containing NF groups linked to carbon in theunsaturated organic compound.

2. In the addition reaction set forth in claim 1, the inert gas isadmixed with the reactant in a proportion to have a partial pressure at25 C. of at least one-half the total pressure at 25 C. of the resultinggaseous reaction mixture and in the range of 124 to 7600 mm. Hgabsolute.

3. In the addition reaction set forth in claim 1, the unsaturatedorganic reactant being a C to C compound, the inert gas being ethane,and the adduct product being bis(NF derivative formed by addition of anNF group to carbon constituents linked together by a double bond in theunsaturated C to C organic compound.

4. In the addition reaction defined in claim 1, the organic reactantbeing ethylene and the adduct being bis(NF )ethane.

5. In the addition reaction defined in claim 1, the or-- ganic reactantbeing 1,3-butadiene.

6. In the addition reaction defined in claim 1, the organic reactantbeing furan.

References Cited UNITED STATES PATENTS 3,342,866 9/1967 Passannante eta1. 260-583 3,354,210 11/1967 Beach et a1. 260563 LELAND A. SEBASTIAN,Primary Examiner US. Cl. X.R. 260453, 563, 583

1. IN THE ADDITION REACTION OF AN UNSATURATED ORGANIC COMPOUND REACTANTIN VAPOR-PHASE WITH N2F4 TO FORM AN ADDUCT, SAID UNSATRURATED ORGANICCOMPOUND CONTAINING 2 TO 6 CARBON ATOMS AND 1 TO 3 DOUBLE BONDS, THEIMPROVEMENT WHICH COMPRISES ADMIXING N2F4 HAVING A PARTIAL PRESSURE OF38 TO 380 MM. HG ABS. AT 25*C. WITH THE UNSATURATED ORGANIC REACTANTHAVING A PARTIAL PRESSURE OF 80 TO 380 MM. HG ABS. AT 25*C. AND WITH ANINERT GAS HAVING A PARTIAL PRESSURE AT 25*C. ABOVE THE COMBINED PARTIALPRESSURES OF THE N2F4 AND ORGANIC REACTANTS TO FORM A GASEOUS REACTIONMIXTURE, REACTING THE REACTANTS IN SAID GASEOUS REACTION MIXTURE AT AREACTION TEMPERATURE IN THE RANGE OF ABOUT 20* TO 200*C., AND RECOVERINGA RESULTING ADDUCT PRODUCT CONTAINING NF2 GROUPS LINKED TO CARBON IN THEUNSATURATED ORGANIC COMPOUND.